1. Field of the Invention
The invention relates to a method for fabricating semiconductor device, and more particularly, to a method of reducing flicker noise of a semiconductor device.
2. Description of the Prior Art
Low frequency, or 1/f noise (also referred to as flicker noise), is a dominant noise source in field-effect transistors (such as MOSFET devices). While not wishing to be bound by theory, the 1/f noise may be caused by carriers, such as electrons or holes, being transiently trapped in the gate dielectric and/or the interface between the gate dielectric and the channel of the transistor. The random translocation of carriers into traps or defect centers, such as silicon dangling bonds, into the gate dielectric and back into the channel, may cause the current through the transistor to fluctuate, which manifests as 1/f noise.
The push toward smaller and faster semiconductor devices has increased the need to reduce 1/f noise. The effect of 1/f noise may be partially reduced by using transistors having large device areas in the initial stages so that 1/f noise does not get amplified to the same extent as the signal in subsequent stages of an amplification circuit. This approach, however, may not prevent 1/f noise from being introduced at later amplification stages in the circuit where smaller transistors are used. Moreover, the dimensions to which such devices can be scaled down may be limited by the necessity for one or more large early stage transistors. Hence, there is a need for new approaches to reducing 1/f noise.